The El Toro "Y" is a freeway interchange in Irvine, California where the Santa Ana Freeway, Interstate 5 (I-5), and the San Diego Freeway merge. South of the El Toro Y, the highway is named the "San Diego Freeway" with the highway designation "I-5." Located in south Orange County, the interchange was named after the nearby city El Toro, and the now-closed Marine Corps Air Station El Toro, located northeast of the interchange.

The Santa Ana Freeway is one of the principal freeways in Southern California, connecting Los Angeles and its southeastern suburbs including the freeway's namesake, the city of Santa Ana. The freeway begins at its junction with the San Diego Freeway, called the El Toro Y, in Irvine, signed as I-5. From there, it generally goes southeast to northwest to the East Los Angeles Interchange, where it takes the designation of U.S. Route 101 (US 101). It then proceeds 2.95 miles (4.75 km) northwest to the Four Level Interchange in downtown Los Angeles. Formerly, the entirety of the route was marked as US 101 until the 1964 highway renumbering, which truncated US 101 to the East Los Angeles Interchange and designated the rest of the freeway as I-5.